1. Field of the Invention
The present invention relates to nucleic acids and proteins encoded thereby. Invention nucleic acids encode a novel family of pituitary-tumor-specific-gene proteins. The invention also relates to methods for making and using such nucleic acids and proteins.
2. Description of the Background
Cancers and tumors are the second most prevalent cause of death in the United States, causing 450,000 deaths per year. One in three Americans will develop cancer, and one in five will die of cancer (Scientific American Medicine, part 12, I, 1, section dated 1987). While substantial progress has been made in identifying some of the likely environmental and hereditary causes of cancer, the statistics for the cancer death rate indicates a need for substantial improvement in the therapy for cancer and related diseases and disorders.
A number of cancer genes, i.e., genes that have been implicated in the etiology of cancer, have been identified in connection with hereditary forms of cancer and in a large number of well-studied tumor cells. Study of cancer genes have helped provide some understanding of the process of tumorigenesis. While a great deal more remains to be learned about cancer genes, the presently known cancer genes serve as useful models for understanding tumorigenesis.
Cancer genes are broadly classified into xe2x80x9concogenesxe2x80x9d which, when activated, promote tumorigenesis, and xe2x80x9ctumor suppressor genesxe2x80x9d which, when damaged, fail to suppress tumorigenesis. While these classifications provide a useful method for conceptualizing tumorigenesis, it is also possible that a particular gene may play differing roles depending upon the particular allelic form of that gene, its regulatory elements, the genetic background and the tissue environment in which it is operating.
Tumor suppressor genes are genes that in their wild-type alleles, express proteins that suppress abnormal cellular proliferation. When the gene coding for a tumor suppressor protein is mutated or deleted, the resulting mutant protein or the complete lack of tumor suppressor protein expression may fail to correctly regulate cellular proliferation, and abnormal cellular proliferation may take place, particularly if there is already existing damage to the cellular regulatory mechanism. A number of well-studied human tumors and tumor cell lines have been shown to have missing or nonfunctional tumor suppressor genes. Examples of tumor suppression genes include, but are not limited to the retinoblastoma susceptibility gen or RB gene, the p53 gene, the deleted in colon carcinoma (DDC) gene and the neurofibromatosis type 1 (NF-1) tumor suppressor gene. Loss of function or inactivation of tumor suppressor genes may play a central role in the initiation and/or progression of a significant number of human cancers.
Anterior pituitary tumors are mostly benign hormone-secreting or non-functioning adenomas arising from a monoclonal expansion of a genetically mutated cell. Pathogenesis of tumor formation in the anterior pituitary has been intensively studied. Mechanisms for pituitary tumorigenesis involve a multi-step cascade of recently characterized molecular events. The most well characterized oncogene in pituitary tumors is gsp, a constitutively active Gasxcex1 resulting form activating point mutations in this gene.
Gasxcex1 mutations occur in about 40% of GH-secreting tumors, and constitutively activated CREB is also found in a subset of these tumors. Although the importance of GSxcex1 mutant proteins in the development of growth-hormone secreting pituitary tumors is well established, only about one third of these tumors contains these mutations, indicating the presence of additional transforming events in pituitary tumorigenesis. Although point mutations of Ras oncogene, loss of heterozygosity (LOH) near the Rb locus on chromosome 13, and LOH on chromosome 11 have been implicated in some pituitary tumors, the mechanism that causes pituitary cell transformation remains largely unknown. Thus, there is a need in the art for additional pituitary derived proteins that are associated with pituitary cell transformation.
The present invention relates to isolated, purified Mammalian-pituitary-Transforming-Gene (PTTG) proteins, formerly named Mammalian Pituitary-Tumor-Specific-Gene (PTSG) proteins. The PTTG proteins of the invention and fragments thereof, are useful in bioassays, as immunogens for producing anti-PTTG antibodies, or in therapeutic compositions containing such proteins and/or antibodies.
This invention also relates to a transgenic non-human mammal that expresses PTTG protein.
The present invention also relates to isolated nucleic acids encoding PTTG (PTSG) proteins of mammalian origin, such as human, rat, etc. The PTTG encoding nucleic acid is also provided in the form of a vector carrying it, as hybridizing probes primers, in host cells carrying them, as anti-sense oligonucleotides, in DNA and RNA forms, and related compositions. The nucleic acid molecules described herein may be incorporated into expression systems known to those of skill in the art. The PTTG nucleic acids are useful as probes for assaying for the presence and/or amount of a PTTG gene or mRNA transcript in a given sample. The nucleic acid molecules described herein, and oligonucleotide fragments thereof, are also useful as primers and/or templates in a PCR reaction for amplifying genes encoding PTTG proteins.
Antibodies that are immunoreactive with invention PTTG proteins are also provided. These antibodies are useful in diagnostic assays to determine levels of PTTG proteins present in a given sample, e.g., tissue samples, biological fluids, Western blots, and the like. The antibodies can also be used to purify PTTG proteins from crude cell extracts and the like. Moreover, these antibodies are considered therapeutically useful to counteract or supplement the biological effect of PTTGs in vivo.
Methods and diagnostic systems for determining the levels of PTTG protein in various tissue samples are provided as well. These diagnostic methods can be used for monitoring the level of therapeutically administered PTTG protein or fragments thereof to facilitate the maintenance of therapeutically effective amounts. These diagnostic methods can also be used to diagnose pathologic and physiological disorders that result from abnormal levels of PTTG protein.